A variable capacity swash plate compressor used in the air-conditioning system of a motor vehicle or the like is provided with a rotating shaft rotatably driven by the rotational force of the engine, a swash plate linked to the rotating shaft so that the angle of inclination can be varied, a compression piston linked to the swash plate, and the like. In the compressor, the stroke of the piston is varied by varying the angle of inclination of the swash plate to control the discharge rate of the coolant gas.
The angle of inclination of the swash plate can be continuously varied by appropriately controlling the pressure inside the control chamber and adjusting the state of balance of the pressure acting on both surfaces of the piston. This is achieved using a capacity control valve opened and closed by electromagnetic force while applying the suction pressure of the suction chamber for drawing in the coolant gas, the discharge pressure of the discharge chamber for discharging the coolant gas pressurized by the piston, and the control chamber pressure of the control chamber (crank chamber) for accommodating the swash plate.
Such capacity control valves are known to be provided, as shown in FIG. 8, with discharge-side passages 73, 77 for providing communication between the discharge chamber and the control chamber; a first valve chamber 82 formed in the middle of the discharge-side passage; suction-side passages 71, 72 for providing communication between the suction chamber and the control chamber; a second valve chamber (operating chamber) 83 formed in the middle of the suction-side passage; a valve body 81 formed so that a first valve part 76 disposed in the first valve chamber 82 and used for opening and closing the discharge-side passages 73, 77, and a second valve part 75 disposed in the second valve chamber 83 and used for opening and closing the suction-side passages 71, 72 are reciprocating in an integral manner at the same time as performing opening and closing in opposite directions of each other; a third valve chamber (capacity chamber) 84 formed in the middle of the suction-side passages 71, 72 nearer the control chamber; a pressure-sensitive body (bellows) 78 disposed in the third valve chamber, and used for exerting an urging force in the elongating (expanding) direction and undergoing constriction in accordance with an increase in the surrounding pressure; a valve seat body (engaging part) 80 provided to a free end of the pressure-sensitive body in the elongation direction, the valve seat body having an annular bearing surface; a third valve part (valve-opening linkage) 79 integrally moving with the valve body 81 in the third valve chamber 84 and having the capability to open and close the suction-side passages by engaging with and disengaging from the valve seat body 80; a solenoid S for exerting electromagnetic driving force on the valve body 81, and the like (hereinafter referred to as “Prior Art 1”; for example, refer to Patent Document 1).
In the capacity control valve 70, in cases in which the control chamber pressure must be changed during capacity control even though a crank structure is not provided in the variable capacity compressor, the discharge chamber and the control chamber can be made to communicate with each other, and the pressure (control chamber pressure) Pc in the control chamber can be adjusted. An arrangement is also possible in which the third valve part (valve-opening linkage) 79 is disengaged from the valve seat body (engaging part) 80 to open the suction-side passages and to provide communication between the suction chamber and the control chamber in cases in which the control chamber pressure Pc increases while the variable capacity compressor is in a stopped state.
Liquid refrigerant (the coolant gas cooled and liquefied during the period of idleness) accumulates in the control chamber (crank chamber) in cases such as those in which the variable capacity swash plate compressor is stopped and then restarted after a long period of idleness. Therefore, the coolant gas cannot be compressed and the discharge rate cannot be maintained at the set level as long as the liquid refrigerant is not discharged.
The liquid refrigerant of the control chamber (crank chamber) must be discharged as quickly as possible immediately after startup to perform the desired capacity control.
When the solenoid S is first turned off and the variable capacity compressor is left in a stopped state for a long time while the second valve part 75 is blocking the communication passages (suction-side passages) 71, 72 in the capacity control valve 70 of Prior Art 1, a state arises in which the liquid refrigerant accumulates in the control chamber (crank chamber) of the variable capacity compressor. In cases in which the variable capacity compressor is stopped for a long period of time, the interior of the variable capacity compressor achieves a uniform pressure, and the control chamber pressure Pc rises substantially above the control chamber pressure Pc and the suction pressure Ps during operation of the variable capacity compressor.
When the solenoid S is turned on and the valve body 81 is started up in this state, the first valve part 76 moves in the closing direction at the same time as the second valve part 75 moves in the opening direction, and the liquid refrigerant in the control chamber of the variable capacity compressor is discharged. The control chamber pressure Pc then constricts the pressure-sensitive body 78, and the third valve part 79 is disengaged from the valve seat body 80 and opened. The state at this time is such that the second valve part 75 opens to open the communication passages (suction-side passages) 72, 71, and the liquid refrigerant inside the control chamber is therefore discharged to the suction chamber of the variable capacity compressor through the communication passages (suction-side passages) 74, 72, 71. When the control chamber pressure Pc reaches or decreases below a preset level, the pressure-sensitive body 78 elastically recovers and elongates, the valve seat body 80 engages with the third valve part 79 and closes, and the communication passages (suction-side passages) 74, 72, 71 are blocked.
However, in Prior Art 1, the structure is such that the pressure-sensitive body 78 is constricted and the third valve part 79 is disengaged from the valve seat body 80 and opened. Problems therefore arise in that the length of the pressure-sensitive body 78 must be increased and other actions taken to increase the opening-valve stroke, and increasing the opening-valve stroke is difficult to accomplish. Specifically, although the capacity control valve of Prior Art 1 can discharge the liquid refrigerant faster than a conventional capacity control valve not configured to be able to open the third valve part 79 (a capacity control valve for discharging the coolant via only a fixed orifice that provides direct communication between the control chamber and the suction chamber), there are limits to the discharge performance.
In view of this, a device provided with a supplementary communication passage 85 on the lateral surface of the third valve part 79 has been proposed by the present inventors (hereinafter referred to as “Prior Art 2”; for example, refer to Patent Document 2), as shown in FIG. 9.
The device of Prior Art 2 has the ability to more quickly discharge the liquid refrigerant and more efficiently discharge pressure during maximum capacity, but problems arise in that flow from the control chamber (crank chamber) to the suction chamber is produced during operation because of a state in which the control chamber (crank chamber) and suction chamber are in constant communication with each other, and the control speed of the swash plate is adversely affected during control of the variable capacity compressor.
FIG. 6 is an explanatory view describing the aperture surface area of the fixed orifice (hereinafter simply referred to as “fixed orifice”) in direct communication with the control chamber and the suction chamber in the above-described Prior Art 1, Prior Art 2, and the present invention; and the aperture surface area of the communication passages (suction-side passages 74, 72, 71) formed from the supplementary communication passage and aperture parts of the third valve part and the valve seat body.
A description will now be given with particular reference to Prior Art 1 and Prior Art 2. For the sake of convenience, s1 in this description is the aperture surface area of the fixed orifice, s2 is the aperture surface area of the third valve part 79 and the valve seat body 80, and s3 is the aperture surface area of the supplementary communication passage 85.
In Prior Art 1, the sum s1+s2 is the aperture surface area during discharge of the liquid refrigerant, and s1 is the aperture surface area during maximum capacity operation, regular control, and minimum capacity operation (hereinafter occasionally referred to collectively as “during control”).
In contrast, an object of Prior Art 2 is to increase the aperture surface area during discharge of the liquid refrigerant, and the aperture surface area during discharge of the liquid refrigerant is increased to s1+s2+s3 by providing the supplementary communication passage 85. However, the supplementary communication passage 85 is constantly open during operation, and the aperture surface area during regular control is therefore also increased to s1+s3. Increasing the aperture surface area during regular control creates the problem that the variation in control chamber pressure Pc relative to the variation in suction pressure Ps is slow, reducing the control speed of the swash plate during regular control. Therefore, the increase in the aperture surface area s1+s3 during regular control is prevented in Prior Art 2 by increasing the aperture surface area s1+s2+s3 during discharge of the liquid refrigerant and reducing the aperture surface area s1 of the fixed orifice as compared with Prior Art 1.